In an optical communication system, optical processing or other optical system, it is often desired to have nonlinear optical device for modulating or switching a first (controlled) optical propagating through the device. Typically, such a device exhibits a variable absorption of the controlled beam, depending upon the intensity of a second (control) optical beam incident upon the device.
In addition to the aforementioned devices operating on the basis of optical absorption, there have been devices operating on the basis of the photo-refractive effect--i.e., variation of refractive index by the control beam, and hence phase modulation by the control beam. Some of these employ a single beam and some employ multiple beams to modify the refractive index of a nonlinear device structure with respect to the controlled beam--and hence to modify either the intensity or the phase of the controlled beam by the further use of known techniques. Those photo-refractive index modulation structures which employ the single beam require undesirably high power to yield commercially significant modifications of the controlled beam, and those structures which employ the two beams to modify refractive index are undesirable because of the complexity arising from the requirement of the two beams. By "refractive index" is meant the ratio of the phase velocity of an optical beam in vacuum to the speed of the beam in a material.
In U.S. Pat. No. 4,546,244 issued to D. A. B. Miller on Oct. 8, 1985, a nonlinear optical device structure, operating on the basis of optical absorption, was disclosed using a GaAs/AlGaAs multiple quantum well structure. That structure, however, requires that external electrical connections be attached to it. The need for such connections is undesirable in certain commercially important uses of such devices--for example, in crosspoint or other arrays. Also, in that structure the speed of operation (maximum repetition rate) is limited by charge carrier recombination time. Therefore it would be desirable to have a nonlinear optical device structure which does not require external electrical connections and whose speed is not limited by charge carrier recombination time.